The production of glazed ceramic tile in accordance with conventional processes requires a period of up to five days from the time the tile is pressed into shape until the final glazed tile product is complete and ready for use. The recent development of improved roller type kilns such as that disclosed in U.S. Pat. No. 3,608,876 to Charles E. Leaich et al, coupled with new techniques in the forming process for ceramic tile have reduced the processing time involved in the formation of glazed ceramic tile from periods of four or five days to a matter of hours; and in some instances less than two hours. Such fast firing processes involving roller kilns of a type similar to that disclosed by the Leaich et al patent involve the continuous passage of a large number of individual ceramic tile over the ceramic hearth rollers of the roller kiln to accomplish a continuous firing process as the tile passes through the kiln. To produce an acceptable glazed ceramic tile product, it is imperative that the firing of the tile be achieved under closely controlled conditions within the kiln, and during passage through the kiln, the tile must be subjected to a number of controlled temperatures for very specific periods of time. To effectively accomplish this firing process, not only must the differing temperature zones throughout the kiln be accurately regulated, but also the tracking of continuous stream of individual ceramic tile across the hearth rollers of the kiln must be closely controlled to achieve the desired firing times for all individual tiles passing through the kiln. Only by providing temperatures and firing times which are substantially uniform for all tiles in the constant stream of tile passing through the kiln will an acceptable and uniform tile product be produced.
Effective fast firing processes for the production of conventional flat surfaced, glazed ceramic tile have been developed and are in use, and such tile constitute 80 to 90% of the tile produced. However, it is still necessary to employ slow firing processes involving a plurality of days to produce ceramic tile trim pieces which constitute the remaining 10 to 20% of the tile sold. These trim pieces come in innumerable geometrical shapes and sizes, and heretofore it has been virtually impossible to accurately track a plurality of such trim pieces through a fast fire roller kiln. While substantially flat surfaced glazed ceramic tile may be maintained in substantially parallel tracks as the tile moves through a fast fire roller kiln so that all tile are subjected to carefully controlled firing times in the different temperature zones of the kiln, the irregular shape of ceramic trim pieces causes these trim pieces to follow irregular paths across the rollers of the kiln. Thus it has been impossible to maintain constant firing times for all trim pieces as they move through various temperature zones within the kiln, for the trim pieces, unlike flat surfaced ceramic tile, refuse to follow a determined path and move in controlled streams. Also, in the fast firing of trim pieces, the deposited glaze on the ceramic rollers of the kiln in certain kiln sections may become even more of a problem than do similar deposits occurring during the fast firing of conventional flat surfaced ceramic tile.
It is the primary object of the present invention to provide a novel method and apparatus for fast firing glazed ceramic tile trim pieces in a roller kiln.
Another object of the present invention is to provide a novel method and apparatus for maintaining glazed ceramic tile trim pieces of irregular geometrical configurations in controlled parallel streams during movement thereof through a roller kiln.
A further object of the present invention is to provide a novel method for fast firing glazed ceramic tile which involves the effective removal of glaze and other foreign deposits from the ceramic rollers of a roller kiln.
Another object of the present invention is to provide a novel kiln roller construction adapted to provide controlled tracking for a plurality of glazed ceramic trim pieces through a roller kiln.
A still further object of the present invention is to provide a novel method and apparatus for producing ceramic tile trim pieces by a fast firing process in a roller kiln while accurately maintaining uniform firing times and temperatures for a plurality of trim pieces moving in a stream through various temperature zones of the kiln.